A horizontal directional drill machine is a common and well-known machine for installing pipes beneath the ground and generally parallel to the surface. These machines are used in many different applications and are available in a wide range of sizes. Typical applications where a horizontal directional drill machine might be used include the installation of fiber optic cables, electrical cables, gas lines, water systems, or sewer systems. Horizontal directional drill machines are commonly rated in terms of pull-back capacity. Some machines for smaller applications have as little as five thousand pounds of pull-back capacity. Other machines are available with a pull-back capacity of as much as one million pounds.
One alternative to a horizontal directional drill machine is the traditional trencher machine. A trencher machine simply digs a trench into the ground, and after (for example) pipe is laid down in the bottom of the trench, the trench is filled and the pipe is buried. The advantage of a horizontal directional drill machine over a trenching machine is that a pipe can be buried in the ground over long distances without digging a trench. Thus, a horizontal directional drill is particularly desirable when a trench would be difficult or too costly to dig. For example, a horizontal directional drill machine finds particularly advantageous application for installing pipes under roadways, where destruction of the road is expensive and inconvenient to travelers, or under a waterway like a river, where trenching would be impossible.
A unique aspect of a horizontal directional drill machine is the special drill head that is attached to the front end of a pipe to be laid. The drill head has an angled shape which allows the operator to change the direction of the pipe after it has entered the ground. Direction changes are achieved by stopping the pipe and drill head rotation and orienting the drill head at a desired angle. Then, by pushing on the drill pipe without rotating it, the drill head and attached pipe will veer in the desired direction. Thus, by effecting directional changes to pipe travel, a pipe might enter the ground at an angle, travel horizontally over a long distance, and exit the ground at another angle. This ability to change the direction of pipe travel also allows the operator to steer the pipe around underground obstacles like boulders.
A completely drilled pipe length is made up of an assembly of shorter pipe lengths that are attached to each other end to end. As the pipe is drilled through the ground successive pipe lengths are attached to the preceding pipe assembly to provide additional length. The additional pipe lengths are stored on the drill in a cartridge, and the bottom pipes in the cartridge are successively attached to the preceding pipe assembly with the aid of a loader. Typically, the cartridge is detachable from the drill body to allow the cartridge to be fully loaded with pipes away from the drill, but this feature is not a necessity for operation of the drill.
Frequently, a need arises during operation of the drill to access the stored pipe lengths in the cartridge while the cartridge is still attached to the drill body. This can occur when a pipe assembly is nearly fully drilled, but a small number of pipe lengths are still required for completion. Instead of detaching the cartridge and attaching a new cartridge fully loaded with new pipe lengths, it is often more convenient to individually load the additional pipe lengths required into the already attached, but empty, cartridge. Additionally, equipment problems can occasionally occur with the drill so that the stored pipes have to be removed one by one from the cartridge while it is still attached to the drill. This situation might arise if the loader assembly fails and the bottom pipe becomes jammed.
Although cartridge and pipe sizes vary widely depending on the size of the drill, the cartridge is commonly between two and three feet deep from its top to the bottom, and the pipes can weigh about seventy-five pounds each. Prior art cartridges support the pipe lengths between side walls that extend longitudinally along the cartridge. These cartridges are loaded and unloaded from the top of the cartridge. Loading and unloading heavy pipes through the top of the cartridge can be difficult and can cause back injuries. Depending on whether the operator is loading or unloading, he must also lower the pipe down into the bottom or lift the pipe up from the bottom of the cartridge through the entire depth of about two to three feet. It is therefore desirable to have a cartridge that would allow easier loading and unloading of the pipes while the cartridge is attached to the drill.